Pregnant women are more likely to form clots than non-pregnant women as pregnancy increases the clotting factors present in the blood. This helps to prevent excess bleeding (hemorrhage) at the time of delivery. Hemorrhage occurs in 5-15% of pregnancies throughout the world, even when delivery is by cesarean section. When hemorrhage occurs the anesthesiologist will normally administer fluids into the woman's vein (intravenously) rapidly to replace the blood that the woman has lost. Two types of fluids are commonly used. One is a salt water solution (saline) and the other is a starch water solution (pentastarch). Use of either or both of these solutions is common during hemorrhage. These same solutions (salt water solution and starch solution) are used at BC Women's Hospital during spinal anesthesia to prevent and treat low blood pressure (a common side effect of spinal anesthesia). This is standard practice whether you are in this study or not. You may also be given, depending on the anesthesiologist's preference, a drug (vasopressor) that causes the blood vessels to become narrow (constrict) to prevent or treat the low blood pressure. Whether you agree to be part of the study or not, your anesthesiologist will be watching your blood pressure closely throughout your operation and if your blood pressure becomes low he/she will treat it as is normally done. Low blood pressure will also occur during hemorrhage. It is therefore important that we determine whether the starch solution, which is more effective than the salt solution in preventing low blood pressure during spinal anesthesia, does or does not affect clotting. Research in non-pregnant adults (male and female) has found that laboratory tests of blood clotting change with these solutions. For saline the evidence in some studies suggests that the blood may clot better than normal while other studies suggest the opposite (does not clot as well). In pregnant and non-pregnant adults the blood does not clot as well with certain starch solutions. The starch solution used at BC Women's Hospital is called pentastarch and no research has looked at its effect on clotting in pregnant women. In non-pregnant adults pentastarch has less effect on clotting than other starch solutions. The purpose of the study is to see how pentastarch (starch solution) and normal saline (water with salt in it) given at the time of spinal anesthesia for elective cesarean section affect the ability of pregnant woman's blood to clot.
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TEG (clotting) parameters at baseline, 5 minutes & 90 minutes post-infusion
Timeframe: During surgery